The present requirements for curtailment of use of fossil forms of energy has led to the increased use of alternative forms, one of which is solar energy. While the radiated energy of the sun is relatively low per unit of area, it may still be harnessed for practical purposes by a solar collector of adequate area. In some instances, a collector may harness all of the energy required for the particular purpose, an example of which is the heating of swimming pools where the desired temperature increase is often small. In others, it may be impractical to collect all of the energy required for a particular purpose and becomes only a substitute for a portion of the energy formerly supplied by fuel. The substituted portion, of course, represents a conservation of such fuel.
In the United States, approximately 14% of the energy used is for residential space and domestic hot water heating. About 29% of this heating load, or about 4% of the total load, is used for domestic hot water. If as much as one half of this load could be supplied by the sun, it would represent a conservation of about 2% of the total energy used in the United States. As will subsequently appear, the present invention can conserve, in each installation, a percentage of energy of such magnitude.
The practicality of heating by a solar energy collector depends, among other things, upon the quantity of heat and ultimate temperature required. For example, the enormous quantity of heat and high temperature thereof required for operating a certain industrial furnace is probably beyond practicality because of solar collector size and necessary elevation of temperature. A domestic hot water heater, however, requires a temperature of the order of only 120.degree.-140.degree. F. and a practical portion of the quantity of heat required may be supplied by a collector of practical size and which may be manufactured for such purpose within economical considerations.